1. Field of the Invention
The present invention relates to a lens apparatus used for an image pickup apparatus such as a compact digital camera and capable of performing an extension/retraction operation with respect to an image pickup apparatus body, and more particularly to a lens apparatus which moves a plurality of lens holding members using a plurality of cam groove portions formed on a cam ring.
2. Description of the Related Art
As a lens apparatus as described above, there is a zoom lens barrel disclosed in Japanese Patent No. 3569478. The zoom lens barrel is, as described below, configured to make it easy to assemble the lens holding members onto the cam ring.
The zoom lens barrel includes first and second lens holding members and a cam ring having an inner circumferential surface on which first and second cam groove portions with which cam followers provided on the first and second lens holding members are formed. A first introducing groove portion which introduces a cam follower of the first lens holding member from a first insertion opening to the first cam groove portion is formed in the cam ring. Furthermore, a second introducing groove portion which introduces a cam follower of the second lens holding member from a second insertion opening provided on the end surface to the second cam groove portion is formed in the cam ring.
In assembling the zoom lens barrel, first of all, the cam follower of the first lens holding member is introduced to the first cam groove portion via the first insertion opening and the first introducing groove portion. After that, the cam ring is rotated, and then the cam follower of the second lens holding member is introduced to the second cam groove portion via the second insertion opening and the second introducing groove portion. In order to enable such an assembly, the end portion of the first cam groove portion and the second insertion opening are formed at the same position in a circumferential direction of the cam ring.
As described above, Japanese Patent No. 3569478 discloses a configuration for easily assembling two lens holding members on two cam groove portions (a plurality of cam groove portions are formed in the circumferential direction of the cam ring) which are formed in the cam ring.
However, when three cam groove portions are formed in the cam ring in order to move three lens holding members, three introducing groove portions which introduce the cam follower provided on each lens holding member from each insertion opening to each cam groove portion are also necessary. Therefore, in the configuration as disclosed in Japanese Patent No. 3569478, it is difficult to dispose three cam groove portions efficiently on an inner circumferential surface of the cam ring which has a space limitation.